Problem: ${2 \div \dfrac{9}{10} =}$
Explanation: ${2} \div \dfrac{9}{10}} ={\dfrac{2}{1}} \div \dfrac{9}{10}} $ $~~~~~~~{\gray{\text{Rewrite 2 as }\dfrac{2}{1}}}. $ $\phantom{2 \div \dfrac{2}{3}}} ={\dfrac{2}{1}} \times \dfrac{10}{9}}$ $ ~~~~~~{\gray{\text{Multiply by reciprocal of }\dfrac{9}{10}.}} $ $\phantom{8 \div \dfrac{2}{3}}} ={\dfrac{{2}\times10}}{1\timesD9}} $ $~~~~~~~{\gray{\text{Multiply. }}} $ $\phantom{8 \div \dfrac{2}{3}}} ={\dfrac{20}{9}} $ ${2 \div \dfrac{9}{10} =\dfrac{20}{9}}$ [Wait, can we rewrite the answer as a mixed number?]